PROJECT SUMMARY Obesity is twice as prevalent among occupational drivers than in the general population. Obesity and associated health conditions increase the risk of vehicle collisions and increase the costs and lost work time associated with injuries by 80%. However, effective interventions are scarce. In our prior funding period we demonstrated the efficacy of a weight loss intervention (tertiary prevention) named ?Safety and Health Involvement For Truckers? (SHIFT). Building on this success, we will advance the field further by adapting our technology and tactics for primary prevention of weight gain among mass transit bus operators during their first years of employment. Our competing renewal strategy will also advance organizational science by integrating an effective health intervention with traditional new employee training and socialization processes. Fifty years of epidemiological evidence is clear ? bus driving increases the risk for obesity and health problems, and it is time for interventions. Our preliminary data suggest that new drivers gain substantial weight during their first year. Health disruptive transitions in early years, like long sedentary work hours, shift work, and stress, may also impact costly problems of absenteeism and collisions in the transit industry. However, weight gain prevention interventions are lacking for employees entering obesogenic occupations, and few workplace training and socialization programs for new hires (referred to as onboarding) explicitly address health hazards. Onboarding is a critical socialization process where employees acquire core skill competencies, establish work-supportive social relationships, learn corporate values, and observe and adapt to workplace norms. Thus, the potential for creating long-lasting impacts on both health and safety during this critical period is high. Our effective SHIFT intervention is implemented through a mobile friendly website, and tactics include an incentivized game-like competition that is supported with behavior and body weight logging, computer-based training, and motivational interviewing. In our proposed adaptation ?SHIFT Onboard? (Safety & Health Impact For Transit drivers during Onboarding) will be designed to prevent weight gain among new bus drivers and support their early adjustment and job success. Our primary hypotheses are that relative to usual practice, SHIFT Onboard participants will have (1) superior sleep, eating, and exercise behaviors; and (2) less weight gain. We will also evaluate impacts on new employee adjustment and economic outcomes that are critical to employers; the ultimate adopters of occupational health innovations. Our ability to succeed is bolstered by our unique past success with transportation workers, expertise in organizational onboarding, and strong transit labor and management support. To test our hypotheses, we will conduct formative research followed by a randomized controlled trial. Our 5-year plan will accomplish 3 specific aims: (1) Adapt our proven tactics and pilot SHIFT Onboard for mass transit bus drivers; (2) Determine the efficacy of SHIFT Onboard for preventing weight gain; and (3) Evaluate new employee adjustment and economic impacts of SHIFT Onboard.